A clock generator is used for a filter auto-calibration in many receiver applications, e.g., Digital Video Broadcasting, Handheld (DVB-H), Global Positioning System (GPS), Wireless Local Area Network (WLAN), etc. The receiver needs to obtain an accurate clock frequency for its filter auto-calibration. In some methods, noise in the generated clock signal is a problem, while a large current consumption and chip area usage are problems in other methods. Also, Process, Voltage, and/or Temperature (PVT) variations can incur high mass testing cost.